The effects of residual hip deformity on coronal alignment of the lower extremity in patients with unilateral slipped capital femoral epiphysis

PURPOSE: The aim of our explorative study was to compare the differences in the coronal alignments of the hip, knee and ankle on the slip side and non-slip sides in patients with slipped capital femoral epiphysis (SCFE). METHODS: The study group consisted of 28 patients. On the full-length standing radiographs, measurements of articulo-trochanteric distance (ATD), neck-shaft angle (NSA), femoral offset, hip-knee-ankle axis, femur-tibial angle, mechanical axis deviation ratio (MAD-r), anatomical medial proximal femoral angle (aMPFA), mechanical lateral proximal femoral angle (mLPFA), anatomical lateral distal femoral angle (aLDFA), mechanical lateral distal femoral angle (mLDFA), knee joint line congruency angle, mechanical medial proximal tibial angle (mMPTA), mechanical lateral distal tibial angle (mLDTA), ankle joint line orientation angle (AJOA), and leg length discrepancy (LLD) were performed. The data from the slip side were compared with those from the non-slip side. RESULTS: At skeletal maturity, there were significant differences between the slip side and non-slip side in ATD (p <0.001), NSA (p <0.001), MAD-r (p <0.001), aMPFA (p <0.001), aLDFA (p = 0.03), mLDFA (p = 0.04), mLDTA (p = 0.02), AJOA (p <0.001) and LLD (p<0.001). CONCLUSION: Residual deformity in the proximal femur after epiphyseal slip and premature epiphysiodesis could cause changes in the coronal alignment of the lower extremity. We can add lower extremity alignment examination to follow-up protocol to rule out secondary problems in patients with SCFE. LEVEL OF EVIDENCE: Level III, retrospective comparative study